"Avatar doesn't update" troubleshooting

Instead of waiting for people to report that their avatars don’t update and then tell them to clear their cache and so on, how about a sticky post with step by step instructions for the most common fixes? Something like:

refresh the page

clear your cache

delete your cookies

use a different browser

reinstall your operating system

burn a graphics card at full moon to summon the tech demon and ask him to fix your stuff